Thanks for posting with what worked for you.
The Roku devices that come equipped with the USB power adapter are 5volt, 1amp power adapters. 1.5 amp and 2amp adapters all the better, but needs at least 1amp if supplying/replacing your own adapter.
It is only with the latest release of Roku products that some models no longer include this power adapter in the box. Not a coincidence that more users are now experiencing these power-related issues during setup since many users are now relying on their TV USB power ports to supply the necessary power. (which these ports may or may not be able to produce adequately).
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660x, Premiere+ 3921, Express 4k+ 3941